As you assess Las Vegas resorts and their various venues, the vibe is often not easy to describe. It’s “kind of Rat Pack-like, mixed with a little hipster, and maybe some ex-con.” Or, “The vibe at that place is very Sun City Summerlin, kind of old-school Mel Torme, but also dangerous in a ‘Godfather’ sort of way.”

The Cosmopolitan is a vibe fortress. It is a structure conceived largely on the vibe, as the hip hotel on the Strip. The vibe there is very “Ocean’s Eleven,” blended with some Fred Astaire-Ginger Rogers dipped in a tub of Liberace bling.

At least, that is how I’ve seen the Cosmopolitan over most of its three-year, eight-month run on the Strip. In January, when the hotel opened the restaurant-lounge-bar Rose. Rabbit. Lie. and the accompanying stage show “Vegas Nocturne,” the vibe was paramount to the marketing and word-of-mouth accounts. But “Vegas Nocturne” has closed, a development that not only silenced one of the more inspired shows of the past decade to roll out on the Strip but has sent a ripple of confusion around the Las Vegas market. Even those who have done business with the hotel and the production show have taken to saying that Rose. Rabbit. Lie. itself has closed. Not so.

The hotel’s CEO, John Unwin, reaches back to late 2013 to remind of the Rose. Rabbit. Lie. vibe. At that time, a video was produced and distributed in-house as a way for Unwin to pitch the concept of the “grand social experiment” to the hotel’s owners at the time, Deutsche Bank. The clip showed assorted vintage and vintage-inspired film scenes, swift edits, shots of dancers in gowns and tuxes, of Ray Liotta bursting into the Copacabana Club in “GoodFellas,” Leonardo DiCaprio-as-Howard Hughes striding across the casino floor at the Tropicana Club in Cuba, and of Lenny Bruce scowling from a comedy club stage in the ’60s.

Unwin does allow that the “Vegas Nocturne” closing has caused some confusion, as the two entities were interlocked and presented as complementary. The hotel since has stepped forward to present entertainment in the Rose. Rabbit. Lie. space (where, as I like to say, you can have an order of caviar tacos with a side of tap dancing). Currently, performers range from torch singers to a great house band, dancers of all variety, soul music trotted out with acoustic sets by performers from the area and throughout the country. The showroom/theater space used by “Vegas Nocturne” will feature one-off performances by such acts as soul and R&B singer-songwriters Nick Waterhouse and Eli “Paperboy” Reed.

The hotel has used Las Vegas and national agencies to recruit performers to populate the entertainment lineup. But there is little in the way of specifics as to who is actually appearing on a given night. That is intentional, another way to perpetrate the hotel’s mystique-laden vibe.

“We have felt, from the beginning, that Rose. Rabbit. Lie. would be the brand, rather than the specific entertainer or entertainment,” Unwin says. “We want word to get out on social media that you had to be there, that this is not going to happen the same way tomorrow night.”

That’s all fine, but the climate in Las Vegas has shifted. When the Cosmopolitan opened in December 2010, it was the hip newcomer, drawing attention (and, more important, business) from such in-demographic competitors as the Hard Rock Hotel and Palms. In the first weeks of the hotel’s opening, I was hearing from folks at the Hard Rock that you could fire a cannon through the casino and hit nothing except a glass case displaying a Steven Tyler stage costume. But Hard Rock is moving its feet and has big plans for all of its entertainment venues by the end of this year. And on the north end of the Strip, SLS is due to open Aug. 23, targeting the same type of younger, hipper, more affluent tourist.

Of course, in Las Vegas, the new and hip can swiftly give way to the old and tired. The Cosmopolitan is working diligently to make sure that does not happen to it. Similar to Astaire dancing across a ballroom floor, Cosmo is gliding along, confident and unfettered, owning that uniquely appealing stage — and a vibe you have to experience to define.